This is a complete revision of the first volume of the classic zoology textbook originally written by Professors Parker and Haswell in 1889. A distinguished international team of authors has been drawn together by the late Professor Marshall and by his colleague and successor, Dr. Williams, and the resulting survey provides an up to date and authoritative account of the whole field of comparative inverebrate zoology. This edition is still true to the aims of the original authors in that it treats it zoology inductively, that is, by making detailed "type" descriptions the basis for inroducing more comparative detail. However, the resemblance to earlier editions stops there. For this edition, each chapter has been revised or entirely rewritten by a different author, each of whom is a specialist in his chosen field.